1. Field of the Invention
The invention concerns an apparatus for illuminating a viewing field, for example a specimen field under a microscope, by means of two light sources.
2. Description of the Related Art
Illumination of a specimen field using two light sources is being increasingly utilized in a variety of applications. The reason for the increased usage is the ability to illuminate the specimen with different light wave spectra, for example UV and/or white light, and/or from different directions. This is applicable in particular to dental medicine, in which light of specific wavelengths is used to polymerize plastics.
The use of flexible light guides (also referred to as optical fiber bundles) makes it possible to deliver light in relatively collimated fashion while focusing the majority of the light onto those locations that are to be illuminated. Further, this is possible while positioning heat-generating lamps remotely from the specimen to be illuminated. A common example of such an flexible light guide is called a “multi-arm cable light guide.”
Spectral filters exclude damaging or undesired light wavelengths. In a variety of known illumination apparatuses, such filters may be replaceably mounted or provided on a carrier so that the filter can be pivoted or slid, as necessary, in front of the flexible light guide or in front of the lamp.
Illumination changers (also referred to as “changing apparatuses”) having interchangeable lamps allow a burned-out lamp to be replaced with a spare lamp, so as to minimize the interruption time in the event of a lamp failure. Leica Microsystems' M500™, used in the field of surgical microscopy, includes a microscope and an illumination apparatus mounted on a stand; an flexible light guide extends between the illumination apparatus and the microscope. A single filter, which filters out damaging light wavelengths, is provided between the lamp and the flexible light guide. Two interchangeable lamps are located on a pivotable carrier that can be pivoted from outside by means of a rotary handle. It is possible to switch from one lamp to the other by pivoting the lamp away from the flexible light guide and pivoting the other lamp in front of it. The filter itself is movable and can readily be replaced with other filters.
Interchangeable filter mounts already exist in the context of illumination apparatuses. A known assemblage (OPMI® VISU 2000 of the Carl Zeiss company in Oberkochen) comprises an interchangeable lamp mount on a pivotable base and an interchangeable filter mount that comprises a rotatable disk having orifices in which the interchangeable filters are inserted. The disk is rotatable about a shaft on the housing, in a plane perpendicular to the flexible light guide, so that by rotation of the disk, different filters can alternately be placed in front of the flexible light guide. The rotation is brought about by a linkage that passes beneath the pivotable interchangeable lamp mount and is joined to a rotary knob outside the housing. The base of the interchangeable lamp mount is pivotable in a plane perpendicular to the disk having the interchangeable filters. Thus, there are completely separate assemblages for both the interchangeable lamp mount and for the interchangeable filter mount. Moreover, the two interchangeable lamp mounts have operating elements and linkages that are mutually independent.
The known systems are disadvantageous in many respects. First, apparatuses of this kind generally require two separate illumination systems which are switched and manipulated independently of one another. Second, as the handpiece of the second light source is independent of the microscope, it must be brought manually to the point requiring polymerization. This results in complex manual manipulation of the second light source and, as a rule, necessitates an assistant (if the physician wishes to perform other actions). Third, the independent switchability of the individual light sources increases the operating complexity of the individual light sources. Fourth, easy changing between the two illumination systems is not possible. As a result, for example, with the one illumination system only UV light is available, making precise positioning difficult or impossible because UV light is invisible. And, fifth, illumination apparatuses having interchangeable filters contain a complex linkage for the interchangeable filter mount yielding an undesirably large overall volume for the assemblage.